1. Field of the Invention
The present invention generally relates to an automatic focus control system for a photographic camera normally arranged to function under an ambient light and more particularly, to an improvement of countermeasures to be taken in the case where desired functioning can not be achieved under the ambient light in the automatic focus control system as referred to above.
2. Description of the Prior Art
Conventionally, there has been known an automatic focus control system which includes:
means for sensing a spatial distribution of brightness of an object to provide initial data, including means for receiving light having a plurality of photosensitive elements each capable of accumulating electric charges generated in response to light falling on each of the photosensitive elements, respectively, and means for taking out the electric charges accumulated in each of the photosensitive elements to serially produce electric signals corresponding thereto as the initial data;
means for processing the initial data to provide focusing information descriptive of a focus condition of the objective lens; and
means for generating a driving power to control the focus of the objective lens in accordance with the focusing information.
The known automatic focus control system as described above is originally arranged to function under an ambient light, but there may be considered cases where desired functionings are not available due to reasons such as a low ambient light, etc. As one of the countermeasures for such cases, it has conventionally been proposed to provide means for emitting a supplementary light in case the system is not satisfactorily operable under an ambient light.
The prior art system as described above further has various other problems to be solved, the elimination of which has been strongly requested up to the present.